About Pregnancy

Pregnancy is the term used to describe the period in which a fetus develops inside a woman's womb or uterus.

Pregnancy usually lasts about 40 weeks, or just over 9 months, as measured from the last menstrual period to delivery. Health care providers refer to three segments of pregnancy, called trimesters. The major events in each trimester are described below.1


  1. Office on Women's Health. (2010). Stages of pregnancy. Retrieved May 20, 2016, from http://womenshealth.gov/pregnancy/you-are-pregnant/stages-of-pregnancy.html
  2. American College of Obstetricians and Gynecologists (ACOG). (2020). Patient education: How your fetus grows during pregnancy. Retrieved December 30, 2020, from https://www.acog.org/store/products/patient-education/pamphlets/pregnancy/how-your-fetus-grows-during-pregnancy external link
  3. Stoll, B. J., Hansen, N. I., Bell, E. F., Shankaran, S., Laptook, A. R., Walsh, M. C., et al. (2010). Neonatal outcomes of extremely preterm infants from the NICHD Neonatal Research Network. Pediatrics, 126, 443–456. PMID: 20732945
  4. Spong, C. Y. (2013). Defining "term" pregnancy: Recommendations from the Defining "Term" Pregnancy Workgroup. JAMA, 309(13), 2445–2446. Retrieved October 28, 2013, from http://jama.jamanetwork.com/article.aspx?articleID=1685467 external link
  5. Centers for Disease Control and Prevention. (n.d.). CDC WONDER: About natality, 2007-2014. Retrieved May 20, 2016, from http://wonder.cdc.gov/natality-current.html
  6. ACOG Committee on Obstetric Practice and Society for Maternal-Fetal Medicine. (2013; Reaffirmed 2015). Committee Opinion No. 579. Definition of term pregnancy. Retrieved May 20, 2016, from https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/11/definition-of-term-pregnancy external link
  7. NICHD. (2013). Carrying pregnancy to 39 weeks: Is it worth it? Yes! Retrieved July 8, 2016, from https://www.nichd.nih.gov/news/resources/spotlight/Pages/013113-NCMHEP-videos.aspx
  8. NICHD. (2013). Redefining the term. Retrieved July 8, 2016, from https://www.nichd.nih.gov/news/resources/spotlight/Pages/102413-redefining-term.aspx
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